where to plug this card to get good capture in small PCI express slot or big PCI express slot? Thanks

The card needs a 4x slot.

You need to look at the specifications of your motherboard to determine which slot is capable of 4x, preferably without causing another card to drop to a slower speed. If you have no available PCIe lanes for this card, the motherboard will usually reduce your GPU to 8x, and use 4 of the 8 freed up lanes for the 4x card. That said, since Edius is very CPU intensive and doesn't rely much on GPU, reducing your GPU from 16x to 8x will probably not be noticeable in Edius, but could cause performance issues with any programs you have that require heavy GPU usage.

The physical size of the slot will only dictate that the slot is physically capable of a certain maximum speed, but does not dictate if it is implemented at that speed with the electronics. For example, the long 16x slots can be hooked up electronically by the board manufacturer to work at 16x, 8x, 4x, 2x, or 1x, but since it is physically a 16x slot, just looking at the size of the slot doesn't tell you.

I have asrock z97 etreme6, which PCIe lanes i need to plug this card in? Thanks

I am not at a computer to look right now, doing this from my phone, so you might want to confirm yourself, but if you look at the manual, the board layout and expansion slot specs, should tell you which is a 4x slot. Based on what I am looking at, you only have one choice, slot 4, (the one in the middle of the board), which is an 8x slot. It will make the upper 16x slot 2 work at 8x. All other slots are either 2x or 1x.

BernH, But the size of the card smaller than lane Pcie4, is it still ok?

The size of the slot is not the relevant thing, unless it is too small for the card, in which case it will not work. As I said above, the physical size only dictates what speed the slot could possibly be configured for, not what it is configured for. What is relevant is the speed that the slot operates at.

The card needs an x4 capable slot. The only slots that are listed as operating at x4 or higher speeds are slots 2 and 4 which share 16 (x16) PCIe lanes. Assuming you have a graphics card in slot 2 the only option left is slot 4. With nothing in slot 4, slot 2 runs at x16, but when something is in slot 4, they both run at x8, unless, as noted below, you have an M2 drive, in which case they operate at x8 and x4 speeds, dedicating 4 lanes (x4) to the M2 drive. All the other slots are either physically too small, which means they run at x1 or x2, or are physically an X16 slot but running at x2 like slot 5.

*If M2_1 slot is occupied, PCIE2 slot will run at x8 mode, and PCIE4 slot will run at x4 mode.

**mini-PCI Express slot is shared with PCIE3 slot.

You will see in my forum signature that I am using an an Intensity Pro 4K and an MSI Z97 Gaming 7 Motherboard which is very similar to yours in terms if the slot configuration. Trust me, this is not something I have never done before.

The main differences in our boards is that the 3 x16 sized slots on my board share the same PCIe lanes, so that the one on mine that is equivalent to your slot 5 is an x4 slot instead of an x2 slot, but using it would force the one on mine that is equivalent to your slot 4 to drop to x4 speed and my slot 2 to drop to x8, and I have 2 more x1 slots.

The manufacturers use these x16 slots in a shared configuration for implementation of nVidia SLI or AMD CrossFire graphics card setups, where the cards are physically an x16 card, but when installing more than one in a system, the cards electronically divide the 16 PCIe lanes that are normally used for a single graphics card between the two cards, causing each one to operate at x8, or as on my board if 3 cards are in use, x8, x4 and x4

The x1, x2, x4, x8, x16 ratings for PCIe are the number of parallel data lanes that are required/available. If the card requires x4, why would you think an x2 capable slot would be ok? It may physically fit, but it will not operate correctly, as you are only supplying it with half of the data lanes it needs.

I don't mean this to sound nasty, but all of this information is readily available on the specification pages for your hardware. If you either don't understand this information, or can't be bothered to look it up, you need to listen to the advice and explanations I or others are giving you, and stop fighting us on it.